Ca Mg Salinity Normal, KH dropping like a stone, pH little high

[Bryn]

Ca 420
Mg 1350
Salinity 1.026
pH 8.7
KH trying to keep at 9.0, but dropping to 6.8 in 18 hours
On July 14th NO3 15ppm (Red Sea), PO4 0.24 (Hanna)
Reef Crystals


I check my KH via the Hanna checker and Red Sea, they show similar results.

This is a newly cycled 40G breeder with one inch of sand, 20lb of rock, and MacroAlgae.

Hypnea pannosa
Coralline Cluster
Gracilaria hayi
Cladophora prolifera

All are growing well. Tank has a slight Diatom bloom and a green algae bloom with a touch of red cyno.

Been using BRS two part to try and keep keep my KH up, from my notes I'm having to does anywhere from 50 - 100ml of soda ash a day to keep it at 9.0

Would be interested in any thoughts about what is draining the KH, or if this is a normal amount. I understand that this is a little different as it is purely a Macro-algae tank, not a Refugium connected to a DT, something that most people don't normally have and contribute Ca Mg and KH drain to their corals, but I only have Macroalgae.

Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Coralline algae can suck up more than 2 dKH per day of growing rapidly. But if the tank does not have a lot, then that is probably not the cause of the demand.

How are you adding alk? How much per day in dKH and how are you calculating it?

 

[Bryn]

Calculating the alk using the BRS (Bulk Reef Supply) calculator, as well as using there two part, using tank size of 35g, increase of 1.4dKH comes out to 98ml. I'm adding this in the morning bolus. I do have a clump of Coralline Cluster which is 4inches x 4inches x 1inch high. This is basically Coralline algae, maybe this is the culprit.

Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Between that and otehr demands, it certainly might be accurate.

Be sure to add the alk to a high flow area so it mixes in rapidly.